Email
Chat with tutor
logo

Ask Questions, Get Answers

X
 
Answer
Comment
Share
Q)

In an AP, the $\; 4^{th}\;$ term is $36$. The$\; 21^{st}\;$ term is $108$ more than the $\;9^{th}\;$ term. What is the first term a and the common difference $d$?

$\begin{array}{1 1} a=15,d=12 \\ a=9,d=9 \\ a=5,d=10 \\ a=3,d=21 \end{array}$

1 Answer

Comment
A)
Answer : (b) a=9 , d=9
Explanation :
$The\;4^{th}\;term\;a_{4}=a+3d=36$
$The\;9^{th}\;term\;a_{9}=a+8d$
$The\;21^{st}\;term\;a_{21}=a+20d=108+a+8d\;{108\;more\;than\;a_{9}}$
$Therefore\;20d-8d=108$
$12d=108$
$d=9$
$a=36-3d=36-27=9.$
Help Clay6 to be free
Clay6 needs your help to survive. We have roughly 7 lakh students visiting us monthly. We want to keep our services free and improve with prompt help and advanced solutions by adding more teachers and infrastructure.

A small donation from you will help us reach that goal faster. Talk to your parents, teachers and school and spread the word about clay6. You can pay online or send a cheque.

Thanks for your support.
Continue
Please choose your payment mode to continue
Home Ask Homework Questions
Your payment for is successful.
Continue
Clay6 tutors use Telegram* chat app to help students with their questions and doubts.
Do you have the Telegram chat app installed?
Already installed Install now
*Telegram is a chat app like WhatsApp / Facebook Messenger / Skype.
...